Antenna feed waveguide system providing rapid switching between scan and tracking modes of operation



RGEERT 0R, BY MCA' GOODMAN, JR.

ATT-ORNEY I6 @e d 95/ o eene Lurxeberg TYPe Le 5 5 l A, .h 3 e l im on, w, w u h R S G 3 MN II DK IC VA ROM JR PDN NMMm AE T Mwwm VLAE DSMMWP. OE O ODMF .GMEO GWS .ETE MVMD G RDN EI Em Fn Aw ws l E n m IU A MW F 5 9 4 .AJ 6 l 2 9 .rum l W 9 6 9 mm 2 4 L 1 M l d. e m l 8 5mm@ U Oct.. 19, 1965 R. M. Goo AN, JR 3,213,455

ANTENNA FEED WAVEGUIDE TEM PROVIDING RAPID SWITCHING BETWEEN SCAN AND TRACKING MODES OF OPERATION Filed May 27, 1965 3 Sheets-Sheet 2 FIG. 2

INVENTOR, ROBERT MCA. GOODMAN, JR.

BMW @fp/bw? Oct. 19, 1965 R. M. GOODMAN, JR 3,213,455

ANTENNA FEED WAVEGUIDE SYSTEM PROVIDING RAPID SWITCHING BETWEEN SCAN AND TRACKING MODES OF OPERATION Filed May 27, 1963 3 Sheets-Sheet 5 FIG. 3

INVENTOR, ROBERT MCA. GOODMAN, JR. BY

A TTFWNE Y United States Patent O 3,213,455 ANTENNA FEED WAVEGUIDE SYSTEM PRGVID- ING RAPID SWITCHING BETWEEN SCAN AND TRACKING MODES F OPERATION Robert M. Goodman, Jr., Marietta, Ga., assigner to the United States of America as represented by the Secretary of the Army Filed May 27, 1963, Ser. No. 283,647 Claims. (Cl. 343-754) This invention relates to microwave antenna systems and more particularly to an antenna feed waveguide switching system to provide rapid transfer between two modes of operation.

In radar tracking systems, it is sometimes required to effect .a rapid transfer between two modes of operation, as for example, between a scan or Search mode and a searchlight or track mode. Such systems usually employ geodesic Luneberg type lens antennas and are capable of operating in a scan mode and, on command, are capable of being switched to a searchlight mode for observing selected targets at any prescribed azimuth and range. Heretofore, this function involved a single antenna feed capable of operation in both modes. To accomplish this, the feed is accelerated to the rotational speed required for the scan or search mode and rotates at that speed while scanning. Transfer to the searchlight or track mode is accomplished by de-accelerating the feed to a stop by the application of a braking torque followed by the rotational shift of the feed to the desired searchlight position. Return to the scan mode is then accomplished by releasing the feed from the searchlight positioning devices and accelerating the feed again to scan speed. Such a system was found to be inadequate inasmuch as it required relatively long time intervals for transfer between modes. A further disadvantage of this type system resides in the fact that associated equipment such as frames, pedestals, trailers, etc., required high strength and rigidity which of course greatly increases the cost of manufacture of such systems. Moreover, high forces, torque and inertias were involved in rapid transfer between modes and, as a result, complicated equipment was needed to perform the required function.

It is an object of the present invention to provide an antenna feed waveguide switching system which overcomes the aforementioned disadvantages.

It is another object of the invention to provide an antenna feed waveguide switching system wherein rapid transfer from scan to searchlight or track mode and, vice versa, may be accomplished with relatively small movement and small mass.

Briefly, the present invention may be described as follows. In a radar system having a single feed source of RF microwave energy and including a geodesic Luneberg type lens antenna provided with a major stationary portion terminating in an annulus arcuate over a prescribed scan angle and a shiftable portion including two alternate arcuate input lips, there is provided means for feeding the RF microwave energy through either one of two alternate paths originating at the arcuate input lips ofthe shiftable portion of the geodesic lens antenna. Included is a first and second concentrically arranged waveguide ring switch comprising a common stationary mem-ber and, respectively, a continuously rotatable driven member and 3,213,455 Patented Oct. 19, 1965 a rotatably positioned member. In addition, there is included discrete shiftable waveguide means respectively positioned intermediate the common stationary ring switch member and the RF feed source. Intermediate the rotatable driven and rotatably positioned members and the stationary major portion of the geodesic lens is the shiftable input part of the geodesic lens which contains the two alternately selected feed paths, each originating with an input lip or feed arc. Means are also included whereby the RF feed energy is selectively circulated through the first waveguide ring switch to the first arcuate input lip of the antenna for providing a scan mode, or through the second waveguide ring switch to the second arcuate input lip of the lens antenna to provide a searchlight mode.

For a better understanding of the invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawing in which:

FIG. l is an assembled cross-section of the present invention;

FIG. 2 is a cut-away isometric drawing, partially in cross-section of the present invention;

FIG. 3 is a diagrammatic representation of the input and output waveguide junctions associated with the ring switches shown in FIG. 1; and

FIG. 4 is a plan view of the rotatably driven member of FIG. l showing the positions of the output waveguide junctions relative to the input lip of the geodesic lens antenna.

Referring now to FIGS. l-3 of the drawing, at 10 there is shown a geodesic Luneberg type lens consisting of a pair of closely nested conducting surfaces of revolutionk which are parallel in the sense that their normal separation is everywhere constant and further comprising a major stationary portion terminated in arcuate annulus 12 and a shiftable, or slideable, portion 88 positioned above annulus 12. Shiftable portion 88 includes two alternate input lips, or feed arcs, 91 and 93 at the top of respective channels 92 and 94. The channels 92 and 94 may be alternately, but not simultaneously, combined with the major stationary portion of the lens to form an integrated geodesic Luneberg type lens antenna as indicated by dashed line representing the geodesic lens mean surface. The alternate input lips 91 aud 93 may be designed for a 30 arc scan angle. Details of shiftable portion 88 will be more fully described below. The two parallel surfaces of the stationary portion of the geodesic lens are referred to as the inner and outer lens parts 14 and 16 respectively, with the inner part being the one with the smaller radius of curvature. The inner part 14 is provided with an upwardly extending annular boss or flange 18 having a circumferential grooved portion on its outer periphery as at 20 to provide one race for a ball bearing 22. The other race for ball bearing 22 is provided by a circumferential groove in the inner periphery of an annular boss 24 aixed to and extending downwardly from a gear driven plate 26. By such an arrangement, plate 26 may be rotated axially about the upwardly extending annular boss 18. As shown, plate 26 is provided with a narrowed outer portion 28 in which there is disposed a circumferential U-shaped channel 30 rectangular in cross-section. The geodesic lens outer part 16 is also provided with .an upwardly extending annular boss or flange 32 having an arcuate grooved portion on the inner periphery thereof as at 34 to provide one race for a ball bearing 36. The other race for ball bearing 36 is provided Iby an arcuate groove in the periphery of an arcuate boss 38 atlixed to and extending downwardly from one end of a sectorial plate 40. With such an arrangement, sectorial plate 40` may be axially rotated within the upwardly extending annular boss 32. The bearings 22 and 36 are arranged .along the saine diametrical plane such that sectorial plate 40 can be positioned concentrically with respect to gear driven plate 26. Plate 40 is provided with a circumferential disposed U-shaped channel 42, rectangular in cross-section, proximal the inner or free edge of the sectorial plate 40. However, for reasons hereinafter explained, a stop means may be provided such that the sectorial plate 40 will be rotated only through an are corresponding to the scan angle of the input lips of the geodesic lens as explained hereinbelow. As shown, the inner or free edge of plate 40 which includes channel 42 and the narrowed portion of plate 26 are substantially the same thickness and coplanar, with the dimension of the respective rectangular channels and 42 being identical. The radial dimension of plate 26 .and plate are such that their opposing peripheries are spaced so that they may be independently rotated without interference therebetween, and the bottom surfaces thereof are spaced from the stationary portion of the geodesic lens terminating at 12. The sectorial plate 40 is thus concentrically arranged with plate 26 and may be rotated by any suitable means through the scan arc concentric with respect to plate 26.

Aflixed to the upper end of annular boss 32 and supported thereon is one end of a xed plate or stator 44 which is adapted to span sectorial plate 40 and the narrowed portion 28 of plate 26. As shown, stator plate 44 is provided with a pair of concentric inverted U-shaped channels 46 and 48, rectangular in cross-section which cover an arc equal to the scan angle coextensive with either of the input lips of lens 10 and are circumferentially arranged and radially spaced such that channel 46 is aligned with channel 30 of gear driven plate 26, and channel 48 is aligned with channel 42 as explained below. The spaced superimposed channels 46 and 30 may thus form a rectangular waveguide annulus section for an arcuate portion equal to the scan angle and, similarly, channels 48 and 42 may form a rectangular waveguide section for the arcuate portion in which they are superimposed. Each of the stator concentric channels 46 and 48 are pr0 vided with respective spaced input waveguide sections 50 and 52 formed in waveguide block 54 which is atiixed to and extends upwardly from stator 44. As shown in FIG. 2 and FIG. 3, each of the input waveguide sections 50 and 52 is respectively coupled to associated channels 46 and 48 by means of offset waveguide junctions 56 and 58 of identical construction. Such offset junctions are fully described in J. S. Hollis Patent No. 3,018,450 for Wave Guide Switch Junction which issued January 23, 1962. superimposed on iixed waveguide block 54 and slideable thereacross is a first moveable waveguide block 60 which is provided with a pair of spaced rectangular wave guide curved sections 62 and 64 arranged such that a single antenna feed 66 may be coupled through respective curved sections 62 and 64 into either input waveguide section 50 or input waveguide section 52 by merely sliding waveguide block 60 to the left or to the right as indicated by the arrow 61. As shown in FIG. 1 and FIG. 2 of the drawing, with block 60 at its extreme right position, waveguide curved section 62 feeds energy from single antenna feed 66 only to input waveguide section 50, and when block 60 is at its other extreme position, waveguide curved section 64 feeds energy from single antenna feed 66 only to input waveguide section 52. Of course, suitable stops may be provided in the usual manner for block 60.

The U-shaped channel 30 in rotatably driven plate 26 is provided with a plurality of uniformly spaced output waveguide feed horns 70 (FIG. 4) to feed the geodesic lens and which are identical in construction to the offset junction described in the above noted Hollis patent. As shown in FIG. 2 and FIG. 3, the output waveguide feed horns are of substantially rectangular cross-section and are oppositely flared as shown at 72. The coupling portion of the output waveguide feed horns comprise an arcuate portion 74 extending in substantial parallelism with the annulus at the region in which coupled and intruding into the annulus to a depth equal to half their widths as shown at 76. The waveguide feed horns are so positioned that their broad walls constitute continuation in the broad walls of the annulus. An aperture 78 in the narrow wall of the annulus and a walled chamber as at 79 is provided in each of the output waveguide feed horns as described in the above noted Hollis patent. Similarly, U-shaped channel 42 in plate 40 is terminated at one end by an output waveguide offset junction 80 similar in construction to the output waveguide feed horns 70. The feed horn portion 82 of junction 80 depends from the bottom surface of plate 40. A rectangular annular waveguide section is provided by the spaced superimposed portions of channels 42 and 48. The arcuate channel 42 is made long enough so that the output waveguide junction 80 is moved through the scan sector defined by the input lips of lens 10. As shown, the respective coupling portions of the output horn 70 associated with channel 30 and the coupling portion of the output horn 82 associated with channel 42 extend in a counter-clockwise direction while coupling portions of waveguide junctions 56 and 58 in input waveguide sections S0 and 52 extend in the clockwise direction.

The slideable or shiftable geodesic lens portion, or block 88, will now be described. As shown, block 88 is positioned intermediate the major stationary portion of the geodesic lens at annulus 12 and the terminals of the output waveguide junctions respectively associated with channels 30 and 42. Block 88 is adapted to be slideably moved across the annulus 12 of the stationary lens portion on a base provided therefore as at 90. As hereinabove described, block 88 is also provided with a pair of curved waveguide sections 92 and 94, each terminated by arcuate slots coextensive with the arc of annulus 12 of lens 10. The upper arcuate slots as at 91 and 93 form the alternate input lips or feed arcs of the geodesic lens and are shown as focal points in FIG. 1. Waveguide block 60 and shiftable lens part 88 may be actuated simultaneously in the same direction by any suitable means well known in the art. The lens input curved sections 92 and 94 are so arranged that either the output from any one of the waveguide junctions 70 associated with channel 30 is coupled to the input lip 91 at the top of 92, or the output from the waveguide junction 80 associated with channel 42 is alternately coupled to the input lip 93 at the top of 94, but not to both outputs simultaneously. This can be accomplished by merely sliding block 88 to the left or to the right as indicated by the arrow 96. Since both blocks 60 and 88 are moved in synchronism, it can be seen that with both blocks at their extreme right positions, a through path is provided from antenna feed 66 to the stationary major part of the geodesic lens at 12 through the outputs derived from channel 30, and with both blocks 60 and 88 at the other extreme position, a through path is provided from antenna feed 66 to the stationary major part of the geodesic lens at 12 through the output derived from channel 42. It is to be understood, of course, that conventional check points are to be provided for the waveguide structures.

In operation, it is to be assumed that the plate 26 is being continuously driven in a clockwise direction and blocks 60 and 88 have been slideably moved to their extreme right position as shown in FIG. l. Under these conditions, the lens 10 may be said to be fed in the scan mode. The split rectangular waveguide ring formed by the rotating channel 30 and the stator channel 46 provide a waveguide ring switch or commutator switch of the type described in the above noted Hollis patent. Energy is transferred from antenna feed 66 through waveguide curved section 62, to input waveguide 50, then through waveguide junction 56 to the split rectangular waveguide ring formed by the rotating channel 30 and stator channel 46. As one output waveguide junction 70 associated with channel 30 passes through the scan arc, energy is fed from waveguide junction 56 through the aforementioned rectangular waveguide ring to the rotating output waveguide junction so that energy leaves the waveguide ring through the one waveguide output junction until the next successive waveguide output junction passes across the scan arc, and the cycle is repeated. The action of the waveguide junction in permitting RF energy to pass in one direction is fully explained in the above-mentioned Hollis patent. The energy derived from the output waveguide junctions 70 associated with channel 30 is fed to the input lip 91 of lens 10 at the top of 92 of block S8 and fed through waveguide curved section 92 of block 88 as one of the output waveguide junctions 70 associated with channel 30 pass across the scan arc. Thus, channel 30 is being continuously rotated to provide a scan feed to the input lip 91 of lens 10 at the top of 92. If during the scan cycle it is desired to spot a preselected target, that is provide a searchlght mode, the transfer can be made by slideably shifting blocks 60 and 88 to the extreme left position indicated by the dotted lines in FIG. 1. By this arrangement, energy from antenna feed 66 is applied through waveguide curved section 64 to input waveguide section 52, the output of which is fed through waveguide junction 58 to the split rectangular waveguide ring formed by stator channel 48 and sectorial plate channel 42. The energy is then fed through the abovementioned split rectangular waveguide ring to the output waveguide junction 80 which may be positioned and stopped anywhere along the scan arc at input lip 93 at the top of 94 to spot scan the target. It can be seen of course, that the mechanical operation of the scan switch is not affected during the operation of the searchlght mode. Transfer from the searchlght mode back to the scan mode can be made without delay by again shifting the blocks 60 and 88 to the extreme right position. Any suitable means such as small double acting solenoids or hydraulic cylinders may be utilized to slide blocks 60 and 88 lback and forth.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is therefore aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a radar system having a single feed source of RF microwave energy; a geodesic Luneberg type lens, said lens including a major stationary portion terminating in an annulus arcuate over a prescribed scan angle and a shiftable portion including two alternate arcuate input lips; means for feeding said RF microwave energy along two alternative paths to said geodesic lens comprising, first and second concentrically arranged waveguide ring switches comprising a common stationary member and, respectively, a continuously rotatably driven member and a rotatably positioned member, a iirst shiftable waveguide means positioned intermediate said stationary member land said RF feed source, and a second shiftable waveguide means including a pair of spaced curved open-ended waveguide sections intermediate said rotatable members and said annulus, the arcuate open ends proximal said rotatable members comprising the arcuate input lips of said lens antenna; said RF feed energy being selectively translated through said iirst waveguide ring switch to one of said arcuate input lips for providing a scan mode when both of said shiftable means are in one extreme position, or through said second waveguide ring switch to the other of said arcuate input lips for providing a searchlght mode when both of said shiftable means are in the other extreme position.

2. The system in accordance with claim 1 wherein said first and second concentrically arranged waveguide ring switches comprise; a common stationary member having two arcuate inverted U-shaped channels concentrically positioned, each arcuate channel being coextensive with respective arcuate input lips, a rotatably driven plate member having a circumferential U-shaped channel congruent with one of said stationary member inverted channels whereby a section of waveguide is formed for superimposed portions of said one inverted channel and said driven plate member channel, and a rotatably positioned plate mem-ber concentric with said rotatably driven plate member and having a U-shaped channel congruent with the other of said stationary member inverted channels whereby a section of waveguide is formed for superimposed portions of said other inverted channel and said rotatably positioned plate member channel.

3. In a radar system having a single feed source of RF microwave energy; a geodesic Luneberg type lens, said lens including a major stationary portion terminating in an annulus arcuate over a prescribed scan angle and a shiftable portion including two alternate arcuate input lips; means for feeding said RF microwave energy along two alternate paths to said geodesic lens comprising, first and second concentrically arranged waveguide ring switches comprising a common stationary member and, respectively, a continuously rotatably driven member and a rotatably positioned member; said first ring switch having .a discrete waveguide input junction and a plurality of spaced output waveguide junctions coupled thereto; said second ring switch having a waveguide input junction and a waveguide output junction coupled thereto; a first shiftable waveguide means intermediate said first and second ring switch input waveguide junctions and said RF feed source, and including a pair of spaced curved waveguide sections, a second shiftable waveguide means intermediate said first and second ring switch output waveguide junctions and said annulus, said second shiftable means including a pair of spaced curved open-ended wavegui-de sections, the arcuate open ends proximal said output waveguide junctions comprising the arcuate input lips of said lens antenna; the waveguide sections in said first and second shiftable means being aligned such that when the shiftable means are simultaneously activated in one direction, a through path for said RF feed energy is provided through said iirst ring switch to one of said input lips to produce a scan antenna mode, and when the shiftable means are simultaneously activated in an opposite direction, a through path for said RF energy is provided through said second ring switch to the other of said input lips to produce a searchlght antenna mode.

4. The system in accordance with claim 3 wherein said tirst waveguide ring switch comprises a stationary plate member and a rotatably driven plate member, said driven member having a circumferential U-shaped channel and said stationary member having two inverted U-shaped concentrically positioned channels each covering an arc coextensive with said arcuate input lips, one of said inverted U-shaped channels being superimposed on the channel in said rotatably driven plate member; and said second waveguide ring switch comprises a rotatably positioned plate concentrically arranged with said rotatably driven plate member and including a U-shaped channel congruent with the remaining inverted U-shaped channel in said stationary plate and superimposed therewith; the output waveguide junctions of said rst waveguide ring switch being equally and circumferentially spaced along and depending from the base of the U-shaped channel associated therewith and extending toward said arcuate lips; the output waveguide junction of said second waveguide ring switch depending from one end of its associated U-shaped channel and extending toward said arcuate lips.

5. In a radar system having a single RF feed source; a geodesic Luneberg type lens antenna having a major stationary portion terminated in an arcuate annulus and a shiftable portion, said shiftable portion including two spaced arcuate input lips and positioned over said annulus; a shiftable waveguide means including two spaced waveguide channels; and means operatively associated with said shiftable waveguide means and said shiftable lens portion whereby RF energy is selected to pass through one of said waveguide channels to one input arcuate lip or, alternately, selected to pass through the other of said waveguide channels to the other of said arcuate input lips, said input arcuate lips and said arcuate annulus being coextensive over a prescribed scan angle.

No references cited.

HERMAN KARL SAALBACH, Primary Examiner. 

5. IN A RADAR SYSTEM HAVING A SINGLE RF FEED SOURCE; A GEODESIC LUNEBERG TYPE LENS ANTENNA HAVING A MAJOR STATIONARY PORTION TERMINATED IN AN ARCUATE ANNULUS AND A SHIFTABLE PORTION, SAID SHIFTABLE PORTION INCLUDING TWO SPACED ARCUATE INPUT LIPS AND POSITIONED OVER SAID ANNULUS; A SHIFTABLE WAVEGUIDE MEANS INCLUDING TWO SPACED WAVEGUIDE CHANNELS; AND MEANS OPERATIVELY ASSOCIATED WITH SAID SHIFTABLE WAVEGUIDE MEANS AND SAID SHIFTABLE LENS PORTION WHEREBY RF ENERGY IS SELECTED TO PASS THROUGH ONE OF SAID WAVEGUIDE CHANNELS TO ONE INPUT ARCUATE LIP OR, ALTERNATELY, SELECTED TO PASS THROUGH THE OTHER OF SAID WAVEGUIDE CHANNELS TO THE OTHER OF SAID ARCUATE INPUT LIPS, SAID INPUT ARCUATE LIPS AND SAID ARCUATE ANNULUS BEING COEXTENSIVE OVER A PRESCRIBED SCAN ANGLE. 